Wikipedia
The nadaswaram, nagaswaram, nadhaswaram or nathaswaram ( Tamil:நாதஸ்வரம்), is a double reed wind instrument. It is a traditional classical instrument originated in Tamil Nadu and also used in Andhra Pradesh, Karnataka, and Kerala (India).
This instrument is "among the world's loudest non-brass acoustic instruments". It is a wind instrument similar to the North Indian shehnai but much longer, with a hardwood body and a large flaring bell made of wood or metal.
In Tamil culture, the nadaswaram is considered to be very auspicious, and it is a key musical instrument played in almost all Hindu weddings and temples of the South Indian tradition. It is part of the family of instruments known as mangala vadya (lit. mangala ["auspicious"], vadya ["instrument"]). The instrument is usually played in pairs, and accompanied by a pair of drums called thavil; it can also be accompanied with a drone from a similar oboe called the ottu.